Generation of tight world space bounding regions

ABSTRACT

Systems and techniques are provided for determining bounding regions for a hierarchical structure for ray tracing. For instance, a process can include obtaining an acceleration data structure, the acceleration data structure including one or more primitives of a scene object. A graph cut can be applied to the acceleration data structure. A set of nodes of the acceleration data structure can be determined based on the graph cut, wherein the determined set of nodes is located adjacent to the graph cut. A world-space bounding box can be generated for the scene object, using the set of nodes determined based on the graph cut.

FIELD

The present disclosure generally relates to graphics processing. Forexample, aspects of the present disclosure are related to systems andtechniques for determining bounding regions (e.g., bounding boxes orother regions) for a hierarchical structure for ray tracing.

BACKGROUND

Ray tracing is a computer graphics technique that can be used togenerate images by tracing paths of light through a three-dimensionalscene, simulating interactions with objects illuminated by lightsources, and determining ray intersections. Ray intersections caninclude ray-primitive intersections or ray-object intersections.Primitives are geometric shapes that can be used to construct or modellarger three-dimensional objects. For example, primitives can includetriangles or polygons.

Ray tracing can be used to generate realistic images, including shadows,of a three-dimensional scene. Scene geometry can be stored in anacceleration data structure that groups scene primitives. Anacceleration data structure can be used to accelerate the process of raytracing by improving the efficiency of ray intersection tests and/orcalculations. For example, a bounding volume hierarchy (BVH) is anacceleration data structure that can group scene primitives in ahierarchical tree of bounding volumes enclosing one or more of the sceneprimitives. Ray tracing can be performed by traversing these hierarchiesto determine ray-primitive and/or ray-object intersections.

BRIEF SUMMARY

In some examples, systems and techniques are described for determiningbounding regions (e.g., bounding boxes or other regions) for ahierarchical structure for ray tracing, such as for a ray tracingacceleration data structure. According to at least one illustrativeexample, a method is provided for ray tracing, the method including:obtaining an acceleration data structure, the acceleration datastructure including one or more primitives of a scene object; applying agraph cut to the acceleration data structure; determining a set of nodesof the acceleration data structure based on the graph cut, wherein theset of nodes is located adjacent to the graph cut; and generating aworld-space bounding box for the scene object, wherein the world-spacebounding box is generated for the set of nodes determined based on thegraph cut.

In another example, an apparatus for ray tracing is provided thatincludes a memory (e.g., configured to store data, such as virtualcontent data, one or more images, etc.) and one or more processors(e.g., implemented in circuitry) coupled to the memory. The one or moreprocessors are configured to and can: obtain an acceleration datastructure, the acceleration data structure including one or moreprimitives of a scene object; apply a graph cut to the acceleration datastructure; determine a set of nodes of the acceleration data structurebased on the graph cut, wherein the set of nodes is located adjacent tothe graph cut; and generate a world-space bounding box for the sceneobject, wherein the world-space bounding box is generated for the set ofnodes determined based on the graph cut.

In another example, a non-transitory computer-readable medium isprovided that has stored thereon instructions that, when executed by oneor more processors, cause the one or more processors to: obtain anacceleration data structure, the acceleration data structure includingone or more primitives of a scene object; apply a graph cut to theacceleration data structure; determine a set of nodes of theacceleration data structure based on the graph cut, wherein the set ofnodes is located adjacent to the graph cut; and generate a world-spacebounding box for the scene object, wherein the world-space bounding boxis generated for the set of nodes determined based on the graph cut.

In another example, an apparatus for ray tracing is provided. Theapparatus includes: means for obtaining an acceleration data structure,the acceleration data structure including one or more primitives of ascene object; means for applying a graph cut to the acceleration datastructure; means for determining a set of nodes of the acceleration datastructure based on the graph cut, wherein the set of nodes is locatedadjacent to the graph cut; and means for generating a world-spacebounding box for the scene object, wherein the world-space bounding boxis generated for the set of nodes determined based on the graph cut.

According to another example, a method is provided for ray tracing. Themethod includes: obtaining a bottom-level acceleration structure (BLAS),the BLAS including one or more primitives of a scene object; calculatinga proxy geometry for a plurality of vertices of the BLAS, the proxygeometry having a first number of vertices that is smaller than a numberof vertices contained in the BLAS; transforming the first number ofvertices of the proxy geometry into a plurality of proxy geometryworld-space vertices; and generating a world-space axis-aligned boundingbox (AABB) for the BLAS, wherein the world-space axis-aligned boundingbox encloses the plurality of proxy geometry world-space vertices.

In another example, an apparatus for ray tracing is provided thatincludes a memory (e.g., configured to store data, such as virtualcontent data, one or more images, etc.) and one or more processors(e.g., implemented in circuitry) coupled to the memory. The one or moreprocessors are configured to and can: obtain a bottom-level accelerationstructure (BLAS), the BLAS including one or more primitives of a sceneobject; calculate a proxy geometry for a plurality of vertices of theBLAS, the proxy geometry have a first number of vertices that is smallerthan a number of vertices contained in the BLAS; transform the firstnumber of vertices of the proxy geometry into a plurality of proxygeometry world-space vertices; and generate a world-space axis-alignedbounding box (AABB) for the BLAS, wherein the world-space axis-alignedbounding box encloses the plurality of proxy geometry world-spacevertices.

In another example, a non-transitory computer-readable medium isprovided that has stored thereon instructions that, when executed by oneor more processors, cause the one or more processors to: obtain abottom-level acceleration structure (BLAS), the BLAS including one ormore primitives of a scene object; calculate a proxy geometry for aplurality of vertices of the BLAS, the proxy geometry have a firstnumber of vertices that is smaller than a number of vertices containedin the BLAS; transform the first number of vertices of the proxygeometry into a plurality of proxy geometry world-space vertices; andgenerate a world-space axis-aligned bounding box (AABB) for the BLAS,wherein the world-space axis-aligned bounding box encloses the pluralityof proxy geometry world-space vertices.

In another example, an apparatus for ray tracing is provided. Theapparatus includes: means for obtaining a bottom-level accelerationstructure (BLAS), the BLAS including one or more primitives of a sceneobject; means for calculating a proxy geometry for a plurality ofvertices of the BLAS, the proxy geometry having a first number ofvertices that is smaller than a number of vertices contained in theBLAS; means for transforming the first number of vertices of the proxygeometry into a plurality of proxy geometry world-space vertices; andmeans for generating a world-space axis-aligned bounding box (AABB) forthe BLAS, wherein the world-space axis-aligned bounding box encloses theplurality of proxy geometry world-space vertices.

According to another example, a method is provided for ray tracing. Themethod includes: obtaining a bottom-level acceleration structure (BLAS),the BLAS including a plurality of object-space vertices for one or moreprimitives of a scene object; transforming each vertex of the pluralityof object-space vertices into a transformed world-space vertex; andgenerating a world-space axis-aligned bounding box (AABB) for the BLASsuch that the world-space AABB encloses each transformed world-spacevertex.

In another example, an apparatus for ray tracing is provided thatincludes a memory (e.g., configured to store data, such as virtualcontent data, one or more images, etc.) and one or more processors(e.g., implemented in circuitry) coupled to the memory. The one or moreprocessors are configured to and can: obtain a bottom-level accelerationstructure (BLAS), the BLAS including a plurality of object-spacevertices for one or more primitives of a scene object; transform eachvertex of the plurality of object-space vertices into a transformedworld-space vertex; and generate a world-space axis-aligned bounding box(AABB) for the BLAS such that the world-space AABB encloses eachtransformed world-space vertex.

In another example, a non-transitory computer-readable medium isprovided that has stored thereon instructions that, when executed by oneor more processors, cause the one or more processors to: obtain abottom-level acceleration structure (BLAS), the BLAS including aplurality of object-space vertices for one or more primitives of a sceneobject; transform each vertex of the plurality of object-space verticesinto a transformed world-space vertex; and generate a world-spaceaxis-aligned bounding box (AABB) for the BLAS such that the world-spaceAABB encloses each transformed world-space vertex.

In another example, an apparatus for ray tracing is provided. Theapparatus includes: means for obtaining a bottom-level accelerationstructure (BLAS), the BLAS including a plurality of object-spacevertices for one or more primitives of a scene object; means fortransforming each vertex of the plurality of object-space vertices intoa transformed world-space vertex; and means for generating a world-spaceaxis-aligned bounding box (AABB) for the BLAS such that the world-spaceAABB encloses each transformed world-space vertex.

In some aspects, one or more of the apparatuses described above is or ispart of a camera, a mobile device (e.g., a mobile telephone or so-called“smart phone” or other mobile device), a wearable device, an extendedreality device (e.g., a virtual reality (VR) device, an augmentedreality (AR) device, or a mixed reality (MR) device), a personalcomputer, a laptop computer, a server computer, or other device. In someaspects, an apparatus includes a camera or multiple cameras forcapturing one or more images. In some aspects, the apparatus furtherincludes a display for displaying one or more images, notifications,and/or other displayable data. In some aspects, the apparatus caninclude one or more sensors, which can be used for determining alocation and/or pose of the apparatus, a state of the apparatuses,and/or for other purposes.

This summary is not intended to identify key or essential features ofthe claimed subject matter, nor is it intended to be used in isolationto determine the scope of the claimed subject matter. The subject mattershould be understood by reference to appropriate portions of the entirespecification of this patent, any or all drawings, and each claim.

The foregoing, together with other features and aspects, will becomemore apparent upon referring to the following specification, claims, andaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Illustrative aspects of the present application are described in detailbelow with reference to the following drawing figures:

FIG. 1 illustrates an example of a ray tracing process, in accordancewith some examples;

FIG. 2A illustrates an example of bounding volumes including one or moreprimitives representing portions of surfaces in a scene, in accordancewith some examples;

FIG. 2B illustrates an example of a bounding volume hierarchy (BVH)organizing the bounding volumes of FIG. 2A, in accordance with someexamples;

FIG. 3A illustrates an example of a scene object and an object-spacebounding volume enclosing the scene object, in accordance with someexamples;

FIG. 3B illustrates an example of a world-space bounding volumeenclosing the object-space bounding volume and scene object of FIG. 3A,in accordance with some examples;

FIG. 4 illustrates an example of an acceleration data structureincluding a top-level acceleration structure (TLAS) and a bottom-levelacceleration structure (BLAS), in accordance with some examples;

FIG. 5A illustrates an example of a relatively loose, non-tight boundingvolume enclosing a scene object, in accordance with some examples;

FIG. 5B illustrates an example of a relatively tight bounding volumeenclosing the scene object of FIG. 5A, in accordance with some examples;

FIG. 6 is a simplified block diagram illustrating an example ray tracingsystem, in accordance with some examples of the present disclosure;

FIG. 7A illustrates an example of a scene object and an object-spacebounding volume enclosing the scene object, in accordance with someexamples of the present disclosure;

FIG. 7B illustrates an example of a scene object and a proxy geometryenclosing the scene object, in accordance with some examples of thepresent disclosure;

FIG. 8A illustrates an example of a world-space bounding volumeenclosing the object-space bounding volume and scene object of FIG. 7A,in accordance with some examples of the present disclosure;

FIG. 8B illustrates an example of a maximally tight world-space boundingvolume enclosing a scene object, in accordance with some examples of thepresent disclosure;

FIG. 8C illustrates an example of a tight world-space bounding volumeenclosing the scene object and the proxy geometry of FIG. 7B, inaccordance with some examples of the present disclosure;

FIG. 9A illustrates an example of a graph cut applied across anacceleration data structure, in accordance with some examples of thepresent disclosure;

FIG. 9B illustrates another example of a graph cut applied across theacceleration data structure of FIG. 9A, in accordance with some examplesof the present disclosure;

FIG. 9C illustrates an example of a traversal technique for determininga graph cut to apply across an acceleration data structure, inaccordance with some examples of the present disclosure;

FIG. 9D illustrates another example of a traversal technique fordetermining a graph cut to apply across an acceleration data structure,in accordance with some examples of the present disclosure;

FIG. 9E illustrates another example of a traversal technique fordetermining a graph cut to apply across an acceleration data structure,in accordance with some examples of the present disclosure;

FIG. 10 is a flow diagram illustrating an example of a process forgraphics processing, in accordance with some examples of the presentdisclosure; and

FIG. 11 is a block diagram illustrating an example of a computing systemfor implementing certain aspects described herein.

DETAILED DESCRIPTION

Certain aspects of this disclosure are provided below. Some of theseaspects may be applied independently and some of them may be applied incombination as would be apparent to those of skill in the art. In thefollowing description, for the purposes of explanation, specific detailsare set forth in order to provide a thorough understanding of aspects ofthe application. However, it will be apparent that various aspects maybe practiced without these specific details. The figures and descriptionare not intended to be restrictive.

The ensuing description provides example aspects only, and is notintended to limit the scope, applicability, or configuration of thedisclosure. Rather, the ensuing description of the example aspects willprovide those skilled in the art with an enabling description forimplementing an example aspect. It should be understood that variouschanges may be made in the function and arrangement of elements withoutdeparting from the spirit and scope of the application as set forth inthe appended claims.

Ray tracing is a graphics processing and rendering technique that can beused to produce photorealistic images by modeling light transport tosimulate optical effects. Ray tracing can realistically simulate thelighting of a three-dimensional (3D) scene and its objects by renderingphysically correct reflections, refractions, shadows, and indirectlighting in the two-dimensional (2D) view of the scene.

Ray tracing can be a computationally intensive technique. For example,the computational resources (e.g., compute time) used to ray trace asingle frame can increase with the number of rays that are traced perframe and/or can increase with the computational resources (e.g.,compute time) expended to trace each individual ray. Due to thiscomputational complexity, ray tracing may often be limited to non-realtime uses. Real-time ray tracing has long been sought after for usessuch as rendering video games, virtual reality (VR) and augmentedreality (AR) experiences, etc. Real-time ray tracing has recently becomepossible, using, for example, hardware acceleration units and/orgraphics processing units (GPUs) that can provide parallelization of theunderlying calculations for each individual ray that is projected into ascene.

The number of rays that can be projected into a scene for each frame isoften relatively small, as the rendering time per frame cannot exceedsome maximum amount without losing real-time performance. The imagequality when using real-time ray tracing can be improved by increasingthe number of rays projected into the scene per frame. This can beachieved by increased parallelization (e.g., providing additionalcomputational resources that allow more rays to be tracedsimultaneously). However, hardware upgrades can carry high upfront costsand may be difficult or impossible to retrofit onto existing systems andplatforms.

A scalable and efficient solution that can improve the real-timeperformance of existing ray tracing hardware is desirable. For example,the number of rays projected into the scene per frame can also beincreased by tracing each ray more efficiently (e.g., reducing thecompute time per ray trace operation allows more ray trace operations tobe performed in the same fixed rendering time per frame). As describedin more detail below, systems and techniques are described herein forproviding accelerated ray tracing operations, such as by producing tightworld-space bounding regions (e.g., bounding boxes) at a controlledcomputational cost.

FIG. 1 is a diagram illustrating an example of a ray tracing technique100. As illustrated, a ray tracing system can perform ray tracing bycasting a plurality of rays (e.g., ray 152 a, ray 154 a, and ray 156 a)from a virtual or imaginary view camera 110 (e.g., which determines theview into the 3D scene), through the pixels 140 of a 2D viewing plane,out into the 3D scene. The ray tracing system can then trace the path ofeach ray to determine if the ray reaches back to a light source 120 inthe 3D scene.

In this technique, each ray is projected through a particular pixel ofthe plurality of pixels 140 that are located on the 2D viewing plane. Inthe event a particular ray reaches a light source (e.g., light source120) in the 3D scene, then information from that ray can be used tocontribute to the final color and/or illumination level of the pixel(from the pixels 140) through which the particular ray was projected.For example, when rays projected into the scene intersect with one ormore objects (e.g., such as object 130), color and lighting informationfrom the point(s) of intersection on the object(s) surfaces cancontribute to the final colors and illumination levels of the pixelsassociated with the rays. Similarly, different objects can havedifferent surface properties that reflect, refract, and/or absorb lightin different ways, which can also contribute to the final pixel colorsand/or illumination level. Rays can also reflect off of objects and hitother objects in the scene, or travel through the surfaces oftransparent objects, etc., before reaching a light source (e.g., lightsource 120).

For example, as illustrated in FIG. 1 , ray 152 a is projected into thescene and intersects object 130, resulting in generation of a firstreflection ray 152 b and a second reflection ray 152 c. The firstreflection ray 152 b reaches light source 120 and consequently, cancontribute color or illumination information for rendering theparticular one of the pixels 140 through which ray 152 was projected.The second reflection ray 152 c does not reach light source 120, andconsequently, may not directly contribute color or illuminationinformation back to the pixels 140. A same or similar scenario isillustrated for ray 154 a and its first reflection ray 154 b (whichreaches light source 120) and second reflection ray 154 c (which doesnot reach light source 120), as well as for ray 156 a and its firstreflection ray 156 b (which reaches light source 120) and secondreflection ray 156 c (which does not reach light source 120).

As mentioned previously, each interaction between a ray and an object orsurface within the 3D scene can contribute color and/or illuminationinformation back to the particular pixel through which the ray wasprojected. In some cases, tracing a greater number of interactions perray can provide increased visual fidelity (e.g., quality) of therendered scene at the expense of increased computational cost (e.g.,time). For example, a ray tracing approach that prioritizes speed overquality might calculate or otherwise determine only the first reflectionfor each ray, while a ray tracing approach that prioritizes quality overspeed might determine three or more reflections per ray. In some cases,after observing either a maximum number of reflections or a raytraveling a certain distance without intersection), the ray can cease totravel and the pixel's value can be updated. In some cases, the ray cancease to travel and the pixel's value can be updated based on a raytraveling a certain distance without reflection (e.g., reflection beingone possible outcome of an intersection). In some cases, the number ofrays that are projected through each pixel of the 2D viewing plane canbe adjusted based on a similar tradeoff between computational cost andvisual fidelity.

Ray tracing can therefore become very costly in terms of the time and/orcomputational power that is required to render realistic-looking scenes,based, for example, on the number of rays projected into the scene andthe number of additional rays that are traced for secondary reflectionsand refractions. Due to this computational complexity, ray tracing istypically limited to non-real time uses (e.g., scenes or visual effectsthat could be rendered in advance for film and television). Real-timeray tracing has long been sought after for use cases such as renderingvideo games, virtual reality (VR) and augmented reality (AR)experiences, etc.

Real-time ray tracing has recently become possible and is oftenperformed by hardware acceleration units and/or graphics processingunits (GPUs) that can provide parallelization of the underlyingcalculations for each individual ray that is projected into the scene.The number of rays that can be projected into the scene for each frameis often relatively small, as the rendering time per frame cannot exceedsome maximum amount without losing real-time performance.

The image quality when using real-time ray tracing can be improved byincreasing the number of rays projected into the scene per frame. Thiscan be achieved by increased parallelization (e.g., providing additionalcomputational resources that allow more rays to be tracedsimultaneously). However, hardware upgrades can carry high upfront costsand may be difficult or impossible to retrofit onto existing systems andplatforms. A scalable and efficient solution that can improve thereal-time performance of existing ray tracing hardware is desirable. Forexample, the number of rays projected into the scene per frame can alsobe increased by tracing each ray more efficiently (e.g., reducing thecompute time per ray trace operation allows more ray trace operations tobe performed in the same fixed rendering time per frame).

One example of a ray tracing acceleration technique utilizes tree-basedacceleration structures to improve the efficiency of ray intersectiontests. For example, scenes can be converted into bounding volumehierarchies (BVHs), which are hierarchical tree structures composed ofever-tighter bounding volumes (also referred to as “bounding regions”such as bounding boxes or “axis-aligned bounding boxes” (AABBs)). Forexample, FIG. 2A illustrates an example structure 200 a in which a scenecontaining a plurality of triangle primitives 252 a-252 e is arrangedinto a series of ever-tighter bounding boxes 256 a-256 e. Scenes maycontain hundreds, thousands, or more primitives, but for purposes ofclarity, only the five triangle primitives 252 a-252 e are depicted. Thebounding boxes 256 a-256 e can be AABBs, which are bounding boxes havinga minimized area or volume within which all points of the enclosedprimitives (e.g., triangle primitives 252 a-252 e) may lie. The boundingboxes may be axis-aligned such that the edges of each bounding box 256a-256 e are parallel to a coordinate axis (e.g., the x, y, and z axes).FIG. 2B illustrates an example hierarchical data structure 200 b havingnodes that are associated with the bounding boxes 256 a-256 e andtriangle primitives 252 a-252 e shown in FIG. 2A. The hierarchical datastructure 200 b can be a BVH. For example, a BVH root node 262 a cancorrespond to the bounding box 256 a shown in FIG. 2A; similarly, anintermediate BVH node 262 b can correspond to the bounding box 256 b ofFIG. 2A; intermediate BVH node 262 c can correspond to the bounding box256 c of FIG. 2A, and so on.

A BVH root node (e.g., BVH root node 262 a of FIG. 2B) contains an AABB(e.g., bounding box 256 a of FIG. 2A) enclosing all the individual sceneor object geometry contained in the BVH leaf nodes. Each primitive inthe BVH root node is assigned to either the left or right child node.The child nodes contain the AABBs containing their assigned geometry,and this geometry is likewise assigned to left or right child nodes,recursively until the BVH leaf nodes contain a small number ofprimitives, e.g., four or fewer. Depending on the extent of any scenechanges and/or object deformations, the next and any subsequent framesmay require one or more new BVH build operations or BVH refitting/updateoperations based on the scene changes.

Testing each ray for intersection against every primitive in the scenecan be inefficient and computationally expensive. BVHs can be used toaccelerate ray intersection testing techniques. For example, each raycan be tested for intersection against BVH bounding boxes using adepth-first tree traversal process instead of against every primitive inthe scene. As mentioned previously, bounding boxes encompass or surrounddifferent amounts of scene geometry or primitives and becomeincreasingly tighter with the depth of the BVH tree structure.

Bounding boxes (e.g., AABBs or other bounding boxes) or other boundingregions can be defined with respect to world-space or object-space.World-space can be considered a constant (e.g., the coordinate space ofthe overall 3D scene). Objects can exist in their own coordinate space,which is referred to as object-space (e.g., the coordinate space inwhich the object was modeled or created). For example, FIGS. 3A and 3Bare diagrams depicting object-space and world-space AABBs (axis-alignedbounding boxes) for the same geometry. Here, FIG. 3A illustrates anobject-space AABB 320 of a geometric scene object 310. Scene objects caninclude the 3D or graphical objects that are present in a 3D scene forwhich ray tracing is performed. In some cases, geometric scene objectscan be scene objects that include geometric primitives such astriangles. In some examples, scene objects can include AABBs or otherobject representations. Object-space AABB 320 and scene object 310 areboth shown in the object-space 300 a of the scene object 310. FIG. 3Billustrates the same geometric scene object 310 but transformed into theworld-space 300 b of the scene (e.g., the scene to which scene object310 belongs or is located). A world-space AABB 330 (or other world-spacebounding box) encloses both the object-space AABB 320 and the sceneobject 310.

Ray tracing can utilize a two-level acceleration structure system, suchas a top-level acceleration structure (TLAS) and a bottom-levelacceleration structure (BLAS), as depicted in FIG. 4 . For example, FIG.4 illustrates a TLAS 410 and a BLAS 430, which are described in greaterdepth below.

The TLAS 410 is built in world-space. TLAS primitives are instances ofBLASs, which are defined in object-space. A TLAS can be constructed as aBVH with leaf nodes (including leaf nodes 412, 414, 416, 422, 424, 426,and 428) containing a BLAS. For example, the TLAS leaf nodes 422, 424,426, and 428 each contain or are otherwise associated with one of thetwo BLASs 440 and 460. A translation matrix can be encoded in the TLASleaf node to perform conversion from world-space to object-space and/orvice versa, as described in greater depth below.

A BLAS can be constructed for each object in a scene, referred to as ascene object. For example, FIG. 4 illustrates a BLAS 440 that may beconstructed for a first unique scene object and a BLAS 460 that may beconstructed for a second unique scene object. BLAS 440 includes leafnodes 442, 444, 446, 452, 454, 456, and 458 and BLAS 460 includes leafnodes 462, 464, 466, 472, 474, 476, and 478. BLAS primitives can be thetriangles or the AABBs of procedural primitives used to build the sceneobject. A bottom level BVH is built over the set of these triangles orAABBs of the scene object, with each BLAS leaf node containing a smallnumber (e.g., up to four, five, or some other number) of triangles orAABBs. For example, in the context of FIG. 4 , the BLAS leaf nodes452-458 and 472-478 can each contain some quantity of triangles, AABBs,or other primitives used to build the scene object. In some examples, aBLAS can also be referred to as a “bottom level BVH.” Multiple instancesof the same BLAS can be included in a TLAS. For example, if a TLASincludes a car object, then a BLAS of a tire can be included four times.The same BLAS can also be included in or referenced by multiple TLASs,as illustrated in FIG. 4 .

In some examples, a TLAS can be created using an Object-To-World matrix,which transforms an input represented in object-space coordinates to anoutput representation in world-space coordinates. A World-To-Objectmatrix can apply the transformation in the opposite direction (e.g.,transforming an input represented in world-space coordinates to anoutput representation in object-space coordinates). In some cases, aTLAS can be built over a set of BLASs by using the Object-To-Worldmatrix to compute the world-space AABB of each BLAS (e.g., theworld-space AABB of the BLAS root nodes 442 and 462). A BVH is thenbuilt over these world-space AABBs of the BLAS root nodes and can bereferred to as a top level BVH or the TLAS 410. In some cases, TLAS andBLAS creation can be performed using a similar or identical technique.For example, the same SAH-based (Surface Area Heuristic) algorithm orapproach can be utilized for both TLAS and BLAS construction.

In some cases, the performance of BVH-accelerated ray tracing can dependon the tightness of the world-space AABBs generated for the BLASincluded in or associated with a TLAS leaf node. For example, a tightbounding box will usually outperform a loose bounding box because fewerrays enter the BLAS, and moreover, rays that do enter the BLAS are lesslikely to pass through empty space. FIG. 5A is a diagram 500 aillustrating an example of a relatively loose bounding box 510 a thatencloses a scene object 530. As shown, the bounding box 510 a isconsidered loose as there is a large amount of empty space between theboundary of the bounding box 510 a and the scene object 530. FIG. 5B isa diagram 500 b illustrating an example of a relatively tight boundingbox 510 b that encloses the same scene object 530. As illustrated, thebounding box 510 b is tighter compared to the bounding box 510 a of FIG.5A, as there is very little empty space between the boundary of thebounding box 510 b and the scene object 530.

When a ray intersects a BLAS bounding box, the ray is automaticallychecked for lower-level intersection against each of the constituentprimitives within the BLAS. A ray that hits only empty space within thebounding box surrounding a BLAS therefore represents wastedcomputational work (and increased time/decreased efficiency). In theexample of FIG. 5A, the two rays 522 and 524 both intersect therelatively loose bounding box 510 a, but neither ray actually intersectsthe scene object 530. As such, the ray intersections determined for rays522 and 524 with the loose bounding box 510 a will result in wastedcomputational work, because the rays 522 and 524 in actuality passthrough empty space despite their intersection with the loose boundingbox 510 a.

In the example of FIG. 5B, the same two rays 522 and 524 are shown.Here, because a relatively tight bounding box 510 b is used to enclosethe scene object 530, neither of the two rays intersect with thebounding box 510 b. Therefore, unlike when loose bounding box 510 a wasused to enclose scene object 530, neither of the rays 522 and 524 willresult in an intersection with the bounding box 510 b and thus avoidswasted computational work.

Reducing wasted computational resources by generating tighterworld-space bounding boxes is desirable. World-space bounding boxes caninclude bounding boxes (e.g., AABBs) with coordinates given inworld-space, rather than in object-space or other coordinate systems. Insome cases, a world-space bounding box can be represented as anobject-space bounding box by transforming its world-space coordinates toobject-space coordinates (e.g., using a World-to-Object matrix).However, computing tighter world-space bounding boxes is itselfassociated with a computational overhead that may be incurred each timean updated volume (e.g., BVH) or new volume (e.g., BVH) is generated inresponse to scene changes between frames. In this case, generating tightworld-space bounding boxes for TLAS leaf nodes at a controlledcomputation cost becomes more desirable.

Systems, apparatuses, processes (also referred to as methods), andcomputer readable media (collectively referred to as “systems andtechniques”) are described herein that can provide accelerated raytracing operations by producing tight world-space bounding regions(e.g., bounding boxes such as AABBs) at a controlled computational cost.Bounding boxes will be used herein as examples of bounding regions.However, any type of bounding regions can be used that are notnecessarily “boxes,” such as polygons, circles, ellipses, or other shapeof bounding region. In some aspects, tight world-space bounding boxescan be determined using one or more ray tracing acceleration datastructures. In some examples, the ray tracing acceleration datastructure can include a bounding volume hierarchy (BVH) and/or ahierarchical tree. Different approaches to calculating world-spacebounding boxes can offer different tradeoffs between computationaloverhead and ray tracing performance, as will be described in greaterdepth below.

FIG. 6 is a diagram illustrating an example ray tracing system 600, inaccordance with some examples of the disclosure. The ray tracing system600 can implement the systems and techniques disclosed herein, includingaspects associated with FIGS. 7A-9E. The ray tracing system 600 canperform various tasks and operations such as, for example, ray tracingtasks and operations (e.g., ray-primitive intersection, ray-boundingvolume intersection, ray-AABB intersection, acceleration data structureconstruction and/or updating, rendering, etc.).

In the example shown in FIG. 6 , the ray tracing system 600 includesstorage 602, compute components 610, a ray tracing engine 620, anacceleration data structure engine 622, and a graphics processing engine624. It should be noted that the components 602 through 624 shown inFIG. 6 are non-limiting examples provided for illustration andexplanation purposes, and other examples can include more, less, and/ordifferent components than those shown in FIG. 6 . For example, in somecases the ray tracing system 600 can include one or more displaydevices, one more other processing engines, one or more other hardwarecomponents, and/or one or more other software and/or hardware componentsthat are not shown in FIG. 6 . An example architecture and examplehardware components that can be implemented by the ray tracing system600 are further described below with respect to FIG. 11 .

References to any of the components of the ray tracing system 600 in thesingular or plural form should not be interpreted as limiting the numberof such components implemented by the ray tracing system 600 to one ormore than one. For example, references to a processor in the singularform should not be interpreted as limiting the number of processorsimplemented by the ray tracing system 600 to one. One of ordinary skillin the art will recognize that, for any of the components shown in FIG.6 , the ray tracing system 600 can include only one of such component(s)or more than one of such component(s).

The ray tracing system 600 can be part of, or implemented by, a singlecomputing device or multiple computing devices. In some examples, theray tracing system 600 can be part of an electronic device (or devices)such as a desktop computer, a laptop or notebook computer, a tabletcomputer, a set-top box, a smart television, a display device, a gamingconsole, a video streaming device, an IoT (Internet-of-Things) device, asmart wearable device (e.g., a head-mounted display (HMD), smartglasses, an extended reality (XR) device (e.g., a VR headset orhead-mounted display (HMD), an AR headset, HMD, or glasses, etc.), orany other suitable electronic device(s).

In some implementations, the storage 602, compute components 610, raytracing engine 620, acceleration data structure engine 622, and graphicsprocessing engine 624 can be part of the same computing device. Forexample, in some cases, the storage 608, compute components 610, raytracing engine 620, acceleration data structure engine 622, and graphicsprocessing engine 624 can be integrated into a smartphone, laptop,tablet computer, smart wearable device, gaming system, and/or any othercomputing device. In other implementations, the storage 602, computecomponents 610, ray tracing engine 620, acceleration data structureengine 622, and graphics processing engine 624 can be part of two ormore separate computing devices. For example, in some cases, some of thecomponents 602 through 624 can be part of, or implemented by, onecomputing device and the remaining components can be part of, orimplemented by, one or more other computing devices.

The storage 602 can be any storage device(s) for storing data. Moreover,the storage 602 can store data from any of the components of the raytracing system 600. For example, the storage 602 can store data from thecompute components 610, data from the ray tracing engine 620, data fromthe acceleration data structure engine 622, and/or data from thegraphics processing engine 624. In some examples, the storage 602 caninclude a buffer for storing data for processing by the computecomponents 610.

The compute components 610 can include a central processing unit (CPU)612, a graphics processing unit (GPU) 614, a memory 616, and/or one ormore hardware accelerator components 618. In some implementations, thecompute components 610 can include other processors or computecomponents, such as one or more digital signal processors (DSPs), one ormore neural processing units (NPUs), and/or other processors or computecomponents. The compute components 610 can perform various operationssuch as ray-primitive intersection, ray-bounding volume intersection,ray-AABB intersection, acceleration data structure construction,acceleration data structure updating, scene rendering, rasterization,geometry processing, pixel processing, visibility processing, etc.

The operations for the ray tracing engine 620, the acceleration datastructure engine 622, and the graphics processing engine 624 (and anyother processing engines) can be implemented by any of the computecomponents 610. In one illustrative example, the operations of one ormore of the ray tracing engine 620, the acceleration data structureengine 622, and the graphics processing engine 624 can be executed bythe GPU 614. In some cases, the operations of one or more of the raytracing engine 620, the acceleration data structure engine 622, and thegraphics processing engine 624 can be executed by the CPU 612.

In some cases, the operations of one or more of the ray tracing engine620, the acceleration data structure engine 622, and the graphicsprocessing engine 624 can be executed by a combination of CPU 612 andGPU 614. In some cases, the compute components 110 can include otherelectronic circuits or hardware, computer software, firmware, or anycombination thereof, to perform any of the various operations describedherein.

In some examples, the ray tracing engine 620 can include one or more raytracing Application Programming Interfaces (APIs). In one illustrativeexample, the ray tracing engine 620 can include one or more rayintersection engines. For example, ray tracing engine 620 can includeone or more ray-primitive intersection engines and/or can include one ormore ray-bounding volume intersection engines. In some cases, raytracing engine 620 can include one or more ray-triangle intersectionengines and/or can include one or more ray-AABB intersection engines. Insome examples, the ray tracing engine 620 can implement one or more rayintersection engines using one or more hardware-accelerated ray tracingunits (RTUs) and/or arithmetic logic units (ALUs).

In some examples, the acceleration data structure engine 622 canconstruct or generate one or more acceleration data structures. Theacceleration data structures generated by acceleration data structureengine 622 can be used by one or more of ray tracing engine 620 andgraphics processing engine 624. In one illustrative example,acceleration data structure engine 622 can construct or generate aBounding Volume Hierarchy (BVH). In some cases, acceleration datastructure engine 622 can generate two-level acceleration structures(e.g., an acceleration data structure including a TLAS and one or moreBLASs). The acceleration data structure engine 622 can be implementedusing the CPU 612, the GPU 614, or a combination of the two. In someexamples, the acceleration data structure engine 622 can additionally,or alternatively, be implemented using one or more of the dedicatedhardware accelerator components 618.

In some examples, the graphics processing engine 624 can include agraphics processing pipeline. For example, graphics processing engine624 can include, but is not limited to, one or more of a geometryprocessing stage, a visibility stage, a rasterization stage, and a pixelprocessing pipeline. In some examples, graphics processing engine 624can communicate with or access the memory 616 of the compute components610. Memory 616 can include one or more of a system memory, a framebuffer, a graphics memory, one or more caches, etc.

In some cases, the ray tracing system 600 (e.g., using the ray tracingengine 620, the acceleration data structure engine 622, and/or thegraphics processing engine 624) can obtain an acceleration datastructure that includes one or more primitives of a scene object. Forexample, the ray tracing system 600 can obtain the acceleration datastructure from storage 602 and/or memory 616. In some cases, theacceleration data structure can be generated or constructed using theacceleration data structure engine 622.

When the ray tracing system 600 obtains an acceleration data structure,the ray tracing engine 620 can apply a graph cut to the accelerationdata structure. A graph cut is a partition of the vertices of a graphinto two disjoint subsets (e.g., a graph cut divides the vertices of thegraph are into a first subset and a second subset, where no vertices arepresent in both the first subset and the second subset) In someexamples, the acceleration data structure engine 622 can apply a graphcut to the acceleration data structure. In some cases, the ray tracingengine 620 and the acceleration data structure engine 622 can work incombination to apply a graph cut to the acceleration data structure.

In some aspects, the ray tracing system 600 (e.g., using the ray tracingengine 620, the acceleration data structure engine 622, and/or thegraphics processing engine 624) can determine a set of nodes of theacceleration data structure based on the graph cut. The set of nodesdetermined by the ray tracing system 600 can be located adjacent to thegraph cut, as will be described in greater depth below with respect tothe example graph cuts illustrates in FIGS. 9A and 9B. In some examples,a set of nodes adjacent to a graph cut can be located immediately abovethe graph cut line (e.g., the graph cut line separates the set of nodesand their child nodes). In some cases, a set of nodes adjacent to agraph cut can be located immediately below the graph cut line (e.g., thegraph cut line separates the set of nodes and their parent nodes). Insome examples, the ray tracing system 600 can determine the set of nodesbased on the graph cut using the ray tracing engine 620 and/or theacceleration data structure engine 622.

In some cases, the ray tracing system 600 (e.g., using the ray tracingengine 620, the acceleration data structure engine 622, and/or thegraphics processing engine 624) can generate a world-space bounding boxfor a scene object. For example, the ray tracing system 600 can generatea world-space bounding box for the scene object that is associated withor included in the obtained acceleration data structure describedpreviously above. In some cases, the world-space bounding boxes can beAABBs. In one illustrative example, the ray tracing system 600 cangenerate the world-space bounding boxes for a set of nodes determinedbased on a graph cut, using the acceleration data structure engine 622(and/or the ray tracing engine 620).

The acceleration data structure engine 622 can obtain one or morerepresentations of a scene object or other scene geometry and generateand/or update a BVH or other acceleration data structure that includesthe scene object or scene geometry. In some examples, the accelerationdata structure engine 622 can obtain representations of a scene objector other scene geometry at least in part from one or more of the storage602 and the memory 616. In some cases, the acceleration data structureengine 622 can obtain representations of a scene object or other scenegeometry from the ray tracing engine 620 (and/or one or more of thecompute components 610).

The acceleration data structure engine 622 can operate overrepresentations of scene objects and scene geometry using bothobject-space representations and world-space representations. In someexamples, the acceleration data structure engine 622 can use one or moreObject-To-World matrices and/or World-To-Object matrices to transformscene objects/geometry from object-space representations intoworld-space representations, and from world-space representations toobject-space representations, respectively.

The following discussion makes reference to the examples of FIGS. 7A and7B, which both depict a scene object 710 in its object-space (e.g.,prior to scene object 710 being transformed into a world-spacerepresentation according to one or more aspects of the systems andtechniques described herein). Scene object 710 can include a pluralityof geometric primitives each having one or more vertices. For instance,scene object 710 can include a plurality of triangles, polygons,procedural primitives, etc. In some examples, scene object 710 can berepresented by and/or stored in an acceleration data structure, such asa BVH or hierarchical tree. For example, scene object 710 can berepresented by or stored in a BLAS, as previously discussed above. TheBLAS containing scene object 710 can itself be contained in, referenced,or pointed to by one or more TLAS leaf nodes. For instance, as notedabove with respect to FIG. 4 , a given BLAS can include a BVH for aunique scene object and therefore may be included in multiple differentTLAS leaf nodes.

As illustrated, FIG. 7A depicts scene object 710 enclosed by anobject-space bounding box 720. In some examples, the object-spacebounding box 720 is an object-space AABB determined for scene object710. In some cases, object-space bounding box 720 can be the BLAS rootnode AABB (e.g., because object-space bounding box 720 includes all ofthe geometry and/or primitives that comprise scene object 710).

FIG. 7B illustrates the same scene object 710 enclosed by a proxygeometry 740. In some examples, the proxy geometry 740 can be a convexhull or a convex hull approximation. In some examples, the proxygeometry 740 can be a bounding box (e.g., AABB). The proxy geometry 740(whether a convex hull, convex hull approximation, or otherwise) can bedetermined based on object-space vertices associated with scene object710. For example, where scene object 710 is stored as a BLAS, proxygeometry 740 can be determined based on the object-space vertices of theBLAS (e.g., proxy geometry 740 can be the convex hull of the BLAS rootnode). In some cases, proxy geometry 740 can be determined based on theobject-space vertices of the geometry and/or primitives stored withinthe BLAS.

The following discussion also makes reference to the example of FIG. 8A,which depicts the object-space view 700 a of FIG. 7A as transformed intoa world-space view 800 a. For example, as depicted in FIG. 8A, sceneobject 710 and its associated object-space AABB 720 have both beentransformed from object-space into world-space (e.g., using anObject-To-World matrix). Transformed scene object 710 and transformedobject-space AABB 720 are further shown as being enclosed within aworld-space bounding box 830.

In some examples, one or more of the world-space view 800 a, the sceneobject 710, the object-space AABB 720, and/or the calculated world-spacebounding box 830 depicted in FIG. 8A can be the same as or similar tothe world-space 300 b, the scene object 310, the object-space AABB 320,and/or the calculated world-space bounding box 330 depicted in FIG. 3B,respectively.

In some examples, the world-space bounding box 830 can be a world-spaceAABB calculated to enclose the world-space transformed vertices ofobject-space AABB 720. Where the world-space bounding box 830 enclosesall of the world-space transformed vertices of object-space AABB 720, itis noted that world-space bounding box 830 will also enclose eachindividual vertex of the geometry and/or primitives included in sceneobject 710 (e.g., because the individual vertices of scene object 710are themselves enclosed by object-space AABB 720).

As mentioned above, in some cases object-space AABB 720 can be a BLASroot node AABB, in which case world-space AABB 830 may be generated forone or more TLAS leaf nodes that contain the BLAS/BLAS root node. In oneillustrative example, the systems and techniques described herein cantransform vertices (e.g., vertices corresponding to the eight corners)of the BLAS root node AABB 720 (e.g., the AABB of the root node of theBLAS associated with the TLAS leaf node) into world-space and place theworld-space AABB 830 around the vertices (e.g., the eight transformedcorners/vertices).

The world-space AABB 830 that is generated from the vertices or cornersof the object-space AABB 720 enclosing scene object 710 can be used(e.g., by the ray tracing system 600) to perform one or more ray tracingoperations. In one illustrative example, continuing in the scenarioabove in which object-space AABB 720 and scene object 710 are stored ina BLAS that is itself associated with a TLAS leaf node, the generatedworld-space AABB 830 can be used (e.g., by the ray tracing system 600)to perform ray tracing operations such as ray intersection tests. Forexample, if a ray projected into the scene is determined by the raytracing system 600 to intersect the world-space AABB 830 generated for aTLAS leaf node, then the BLAS associated with that TLAS leaf node willbe traversed and further ray intersection tests will be performed forthe child nodes and/or leaf nodes of the BLAS; if a ray projected intothe scene is determined by the ray tracing system 600 as notintersecting the world-space AABB 830 generated for a TLAS leaf node,then the BLAS associated with that TLAS leaf node need not be traversed.

As such, it can be desirable to generate a world-space AABB (e.g., suchas world-space AABB 830) that is tight with respect to the actualgeometry or primitives contained within the BLAS or object-space AABBassociated with a TLAS leaf node, as has been described above. However,approaches that generate world-space AABBs for TLAS leaf nodes based ontransforming only the eight corners/vertices of object-space AABB 720into world-space often result in an overly loose (e.g., non-tight)bounding box. World-space AABB 830 is an example of a loose or non-tightbounding box, as world-space AABB 830 can be seen to include significantamounts of empty space beyond the volume occupied by scene object 710and beyond the volume occupied by object-space AABB 720.

As noted above, the ray tracing system 600 can implement the systems andtechniques described herein to provide accelerated ray tracingoperations by producing world-space bounding boxes that are tight to anunderlying scene object and have a controlled computational cost. In oneillustrative example, the ray tracing system 600 can use object-spacerepresentations of scene objects and/or scene primitives to generateworld-space bounding boxes with greater tightness relative to anunderlying scene object, as will be described in greater depth below. Insome examples, the generated world-space bounding boxes can beworld-space AABBs.

In a first approach, the ray tracing system 600 can obtain a maximallytight world-space bounding box for a scene object or other set of sceneprimitives by individually transforming each vertex of the sceneobject/scene primitives from an object-space representation to aworld-space representation. A world-space bounding box subsequentlycalculated over the resulting set of all the transformed world-spacevertices (e.g., the object-space vertices of the scene object that havebeen transformed into world-space representations) will have a maximaltightness relative to the underlying scene object.

FIG. 8B illustrates an example of this first approach. In particular,FIG. 8B is a diagram 800 b illustrating an example of a scene object 710that has been transformed into world-space and enclosed by a maximallytight world-space bounding box 850. In some cases, the maximally tightworld-space bounding box 850 can be an AABB. The scene object 710depicted in FIG. 8B can be the same as the scene object 710 depicted inFIGS. 7A-8A and described above. It is noted that, in comparison to therelatively loose world-space bounding box 830 of FIG. 8A, the maximallytight world-space bounding box 850 of FIG. 8B is computed for the samescene object 710 yet includes significantly less empty space beyond thevolume occupied by scene object 710.

In some examples, the ray tracing system 600 can obtain the maximallytight world-space bounding box/AABB 850 by transforming each vertexassociated with the geometry of scene object 710 from object-space toworld-space, using, for example, an Object-To-World matrix as previouslydescribed above. In one illustrative example, the ray tracing system 600can calculate or otherwise determine the maximally tight world-spaceAABB 850 for a TLAS leaf node. The TLAS leaf node can contain orotherwise be associated with a BLAS that was previously constructed fora given scene object such as scene object 710.

Because ray tracing performance can depend on bounding box or AABBtightness, this first approach of individually transforming each vertexof the scene primitives from object-space to world-space can offer thehighest ray tracing performance as compared to other approachesdescribed herein. In some examples, this first approach may beassociated with a higher computational cost as compared to the otherapproaches described below. This higher computational cost can arise dueto the individual transformation of each object-space vertex into aworld-space vertex, especially as the number of vertices per BLAS orTLAS increases. In some cases, when the BVH associated with a TLASand/or a BLAS is updated or otherwise changed, the first approach maycalculate a new AABB by re-computing individual object-to-world vertextransformations. In some examples, the BVH associated with a TLAS or aBLAS may be updated or otherwise changed frequently (e.g., in responseto a scene change, object deformation, etc.).

As noted above, the first approach of generating world-space boundingboxes (e.g., at TLAS leaf nodes) by individually transforming eachvertex included in a scene object from object-space to world-space canoffer the greatest ray tracing performance, but with higher upfrontcomputational cost of BVH construction. For example, a maximally tightworld-space bounding box such as AABB 850 of FIG. 8B can be associatedwith the quickest completion time or lowest amount of required time toperform ray tracing and/or ray intersection tests, as compared to looseror non-maximally tight world-space bounding boxes (e.g., such as therelatively loose world-space bounding box 830 of FIG. 8A). A maximallytight world-space bounding box such as AABB 850 may also be associatedwith the greatest completion time for BVH construction or computation,since each individual vertex is transformed from object-space toworld-space before the maximally tight world-space bounding box 850 canbe constructed. Therefore, this first approach of generating world-spacebounding boxes by individually transforming each vertex of a sceneobject from object-space to world-space may be used when a relativelylarge time budget is available for BVH construction and a relativelysmall time budget is available for ray tracing operations such as rayintersection tests. Additionally or alternatively, in some cases thefirst approach may be performed when adequate computational resourcesare available for performing such techniques. In some aspects, the raytracing system 600 can dynamically determine which approach to takebased on available time budget and/or available computations resources.

In another illustrative example, the ray tracing system 600 can performa second approach to determine a world-space bounding box (e.g., aworld-space AABB) that is tight to an underlying scene object. Thesecond approach includes determining a proxy geometry for one or morevertices associated with the scene object. After determining the proxygeometry (or an approximation thereof) for the scene object, the raytracing system 600 can calculate or otherwise determine a world-spacebounding box or AABB over the vertices of the proxy geometry using thefirst approach described above. For example, the systems and techniquesdescribed herein can transform each vertex of the proxy geometry fromobject-space to world-space and then calculate the world-space AABB overthe transformed vertices.

An example of this second approach of determining a tight world-spacebounding box based on a proxy geometry determined for a scene object isillustrated in FIG. 8C. As illustrated, FIG. 8C is a diagram 800 cdepicting an example of an Object-To-World transformation of a sceneobject 710 and its associated proxy geometry 740 (or an approximationthereof). In some examples, proxy geometry 740 is computed or otherwisedetermined for object-space vertices included in scene object 710.Subsequently, vertices of proxy geometry 740 can be transformed from anobject-space representation into a world-space representation (e.g.,using an Object-To-World matrix). The transformed world-space verticesof proxy geometry 740 can then be used to calculate or construct a tightworld-space bounding box 870 (e.g., an AABB) that encloses both theproxy geometry 740 and all of the geometry of scene object 710. It isnoted that, in comparison to the relatively loose world-space boundingbox 830 of FIG. 8A, the proxy geometry-based world-space bounding box870 is relatively tight to the same underlying scene object 710 and cantherefore offer improved ray tracing performance and/or speed.

In some examples, scene object 710 can be the same as the scene object710 described above with respect to one or more of FIGS. 7A-8B. In somecases, proxy geometry 740 can be the same as or similar to the proxygeometry 740 previously described with respect to FIG. 7B. For example,the proxy geometry can be a convex hull (or a convex hull approximation)determined over the set of all vertices included in the scene object710. In some cases, other hull geometries and/or proxy geometries can becalculated or approximated over the vertices of scene object 710 withoutdeparting from the scope of the present disclosure.

In some aspects, the determination of proxy geometry 740 may introducean additional computational overhead. However, the additionalcomputational overhead of determining proxy geometry 740 can, in someexamples, be less than the computational overhead of transforming eachvertex of the scene object 710 from object-space to world-space. In someexamples, the initial determination of proxy geometry 740 can reduce thetotal number of vertices of scene object 710 that are ultimatelytransformed from object-space to world-space, and as such, may result ina faster (e.g., shorter) BVH construction time than that associated withconstructing the maximally tight world-space AABB 850 as described abovewith respect to FIG. 8B. In some cases, the world-space bounding box orAABB 870 that can be subsequently calculated over the resulting proxygeometry 740 can have a greater tightness relative to the underlyingscene object 710 than the loose world-space bounding box 830 of FIG. 8Aand a lesser computational cost relative to the maximally tightworld-space bounding box 850 of FIG. 8B.

In another illustrative example, the ray tracing system 600 can performa third approach to determining a world-space bounding box that is tightto an underlying scene object. The third approach includes applying agraph cut across an acceleration data structure associated with theprimitives of the scene object. The ray tracing system 600 can transformvertices of acceleration data structure nodes (e.g., BVH and/or BLASnodes) that are adjacent to or at the graph cut line (e.g., immediatelyabove or below the graph cut line) from object-space to world-space. Aworld-space bounding box generated or constructed for the transformedvertices at the graph cut line can be tight to the underlying sceneobject stored in the acceleration data structure to which the graph cutwas applied.

In some examples, the ray tracing system 600 can use the third approachof applying a graph cut to an acceleration data structure to apply agraph cut across the BLAS associated with a TLAS leaf node, obtain theobject-space bounding boxes (e.g., AABBs) for the BLAS nodes immediatelyabove or below the graph cut line, and transform the vertices of theobject-space AABBs into a set of world-space vertices. The ray tracingsystem 600 can then construct a world-space AABB around the resultingset of transformed vertices and use the world-space AABB as a tightworld-space bounding box for the TLAS leaf node.

An example of this third approach is illustrated in FIGS. 9A and 9B,which depict two different graph cut lines 950 a and 950 b,respectively, applied to the same acceleration data structure. In theexample of FIGS. 9A and 9B, the illustrated acceleration data structure(e.g., acceleration data structure 900 a and acceleration data structure900 b, respectively) can be a BVH and/or a BLAS.

In some cases, when the acceleration data structure is a TLAS and/or aBLAS, a tight world-space bounding box can be obtained based on applyinga graph cut 950 a or 950 b across the bottom level BVH (e.g., BLAS)included in a given TLAS leaf node. A graph cut partitions the nodes ofthe bottom level BVH into two disjoint subsets, such that any path fromthe root node 902 of the bottom level BVH to a leaf node (e.g., 932,933, 934, 935, 936, 937, 928) of the bottom level BVH crosses the graphcut line (e.g., 950 a, 950 b) exactly once. Based on this observation,any graph cut across the bottom level BVH will yield a set of AABBs thatcontain the entire geometry of the scene object or model that isrepresented by the bottom level BVH or BLAS.

For example, with respect to FIG. 9A, the graph cut line 950 apartitions the nodes of acceleration data structure 900 a (e.g., BLAS orBVH) into two disjoint subsets, with a first subset located above graphcut line 950 a and a second subset located below graph cut line 950 b.The first subset of nodes includes a BLAS root node 902 and BLAS childnodes 912, 914, 924, and 926 (e.g., above graph cut line 950 a). Thesecond subset of nodes includes BLAS child node 922 and BLAS leaf nodes928, 932, 933, 934, 935, 936, and 937 (e.g., below graph cut line 950a). The set of AABBs/bounding boxes of the nodes that are immediatelyadjacent to (e.g., either directly above or directly below) graph cutline 950 a contain the entire geometry of the underlying scene objectthat is represented by acceleration data structure 900 a.

With respect to FIG. 9B, the graph cut line 950 b partitions the nodesof acceleration data structure 900 b (e.g., BLAS or BVH) into twodisjoint subsets, with a first subset located above graph cut line 950 band a second subset located below graph cut line 950 b. Because graphcut line 950 b is different from graph cut line 950 a, so too are thedisjoint subsets associated with each graph cut line also different fromeach other. For example, the first subset of nodes created by graph cutline 950 b includes BLAS root node 902 and BLAS child nodes 912, 914,922, and 926 (e.g., above graph cut line 950 b). The second subset ofnodes created by graph cut line 950 b includes BLAS child node 924 andBLAS leaf nodes 928, 932, 933, 934, 935, 936, and 937.

In some cases, the ray tracing system 600 can determine optimal graphcut by applying a cost metric during the traversal or examination of theacceleration data structure(s) associated with the primitives of thescene object. For example, the acceleration data structures can includean acceleration data structure 900 a, 900 b (e.g., as described above)and/or a bottom-level BVH. In some aspects, the ray tracing system 600can determine an optimal graph cut by applying a Surface Area Heuristic(SAH) to treelet growth for a given computational budget. The SAHprovides an estimate of the ray tracing performance of different builddecisions for a BVH or other acceleration data structure. In some cases,the ray tracing system 600 can use the SAH to determine the choice ofgraph cut across a BLAS through an iterative technique in which a rootnode (e.g., the root node 902 of the acceleration data structure 900 a,900 b or the root node of a bottom level BVH otherwise associated with aTLAS leaf node) is placed in a stack and has its child nodes (e.g.,nodes 912-926) selectively expanded based on their SAH until the numberof nodes in the stack reaches a pre-determined computational budget.

FIGS. 9C-9E depict an illustrative example of a technique that can beperformed by the ray tracing system 600 for determining a set of nodes980 that can be used to determine an optimal graph cut across anacceleration data structure 970 (e.g., as described above). In somecases, the acceleration data structure 970 can be a BVH or otherhierarchical tree-based structure. As illustrated, a stack 960 can storeone or more nodes of the acceleration data structure 970. In oneillustrative example, the stack 960 can be part of the memory 616 ofFIG. 6 . As will be explained in greater depth below, traversal of theacceleration data structure 970 to determine the optimal graph cut canbe based at least in part on popping the stack 960 (e.g., taking the topnode or element from stack 960). In some examples, when the traversal ofacceleration data structure 970 reaches a leaf node of the accelerationdata structure 970, the stack 960 can be popped and traversal canproceed to the top node that was popped from stack 960.

In some aspects, after the root node of the acceleration data structure970 (e.g., root node 902 of FIG. 9A and FIG. 9B) has been traversed orplaced in the stack 960, the iterative technique for determining anoptimal graph cut across acceleration data structure 970 can beperformed as follows: 1) pop the stack (e.g., take the top node orelement from the stack) and place the popped node's or element'schildren on the stack; 2) sort the stack by the SAH of each element; and3) repeat until the number of nodes on the stack reaches thecomputational budget.

For example, as illustrated in FIG. 9C, traversal can begin at the rootnode (e.g., node 0) of the acceleration data structure 970. Node 1 andnode 4 are the two children of root node 0, and traversal will proceedfrom root node 0 to either node 1 or node 4. In some embodiments, theselection between the two available child nodes can be based on the SAHas applied to node 1 and node 4. For example, traversal can proceed fromroot node 0 to the child node with the lowest SAH value.

As depicted in FIG. 9C, traversal proceeds from root node 0 to node 4(e.g., in some examples, node 4 is determined to have a lower SAH valuethan node 1). Node 1, as the non-selected or non-visited child node, ispushed to the stack 960. In some cases, node 1 can be pushed to stack960 based at least in part on a determination that the traversal ofacceleration data structure 970 should visit node 1 at some point in thefuture. Stack 960 can be used as a queue or indication of nodes thatwere not selected for traversal but should be visited or traversed inthe future.

After the traversal proceeds from root node 0 to child node 4 (e.g.,after the child node 4 is visited), node 4 can be added to a current setor listing (e.g., to the set of nodes 980) that includes nodes ofacceleration data structure 970 that may be used to determine theoptimal graph cut.

After the traversal has visited or otherwise examined node 4, thetraversal can proceed to one of the children of node 4. As illustratedin FIG. 9C, the children of node 4 are leaf node 5 and leaf node 6.Similar to as was described above, one of the two leaf nodes can beselected for traversal in a next step (e.g., based on the SAH), with thenon-selected leaf node being pushed to stack 960.

In the example of FIG. 9C, leaf node 5 is selected for traversal andleaf node 6 is non-selected (e.g., and leaf node 6 is therefore pushedto stack 960 for traversal in a future step). Traversal proceeds fromchild node 4 to leaf node 5, and leaf node 5 is added to the set ofnodes 980 of acceleration data structure 970 that may be used todetermine the optimal graph cut. As illustrated in FIG. 9C, the set ofnodes 980 currently contains node 4 and node 5.

As illustrated in FIG. 9D, node 4 can be removed from the set of nodes980, based on the addition of its child node 5 to same set of nodes 980.For example, because acceleration data structure 970 is a BVH or otherhierarchical tree structure, the set of nodes 980 can be maintained toavoid the simultaneous presence of a parent node and its child node.

After the traversal has visited or otherwise completed an examination ofnode 5, node 5 can be checked for any child nodes that can be visited ina next traversal step. However, because node 5 is a leaf node of theacceleration data structure 970, no child nodes are available to visitin the next traversal step. In response to no nodes being available tovisit in the next traversal step, the node stored at the top of stack960 can be popped and visited in the next traversal step.

As illustrated in FIG. 9D, node 6 is the node stored at the top of stack960. Traversal can therefore proceed from leaf node 5 to leaf node 6.Popping leaf node 6 from stack 960 can cause the leaf node 6 to beremoved from stack 960 (e.g., leaving node 1 as the new topmost nodestored at the top of stack 960). Leaf node 6 can then be added to theset of nodes 980 that may be used to determine an optimal graph cutacross the acceleration data structure 970. At the end of the traversalstep that visits or otherwise examines leaf node 6, the set of nodes 980contains leaf node 5 and leaf node 6, and the stack 960 contains thechild node 1.

After the traversal has visited or otherwise completed an examination ofnode 6 (e.g., after node 6 has been added to the set of nodes 980), node6 can be checked for any child nodes that can be visited in a nexttraversal step. Node 6 is a leaf node of the acceleration data structure970, and therefore has no child nodes that can be visited in the nexttraversal step. As described above, in response to determining that node6 has no child nodes that can be visited in the next traversal step, thenode stored at the top of stack 960 can be popped and visited in thenext traversal step.

As illustrated in FIG. 9E, node 1 is the node stored at the top of stack960. Traversal can therefore proceed from node 6 to node 1, as is alsoillustrated in FIG. 9E. In response to being popped from the stack 960,node 1 can be removed from the stack 960. Node 1 can then be added tothe set of nodes 980 that may be used to determine an optimal graph cutacross the acceleration data structure 970. After the traversal stepvisits or otherwise examines node 1, the stack 960 is empty and the setof nodes 980 contains three nodes (e.g., node 5, node 6, and node 7).

Although the most recently visited or traversed node (e.g., node 1) hastwo child nodes (e.g., node 2 and node 3), the iterative traversaltechnique described above can terminate without visiting nodes 2 or 3.In one illustrative example, the iterative traversal technique canterminate based on a pre-determined computational budget being reached.For example, the pre-determined computational budget can include amaximum number of nodes or entries that can be stored in then set ofnodes 980 (e.g., if the pre-determined computational budget indicatesthat the maximum number of nodes that can be stored in the set of nodes980 is three, the iterative traversal technique can terminate after theexample of FIG. 9E).

At the end of the iterative technique (e.g., once the pre-determinedcomputational budget is reached), the set of nodes 980 or elements canrepresent an optimal graph cut across the acceleration data structure970 for the given computational budget. The ray tracing system 600 canthen calculate a world-space AABB for the vertices of the BLAS nodesadjacent to the determined optimal graph cut line, as has been describedabove. For example, the world-space AABB can be calculated by applyingan Object-To-World matrix to the vertices of the object-space AABBs ofthe BLAS nodes adjacent to the graph cut line and then building theworld-space AABB over the transformed vertices.

In some aspects, the selection of a graph cut line to apply across theBLAS (e.g., bottom level BVH) of a TLAS leaf node can be used to obtaina desired degree of granularity or tightness in the world-space boundingbox that is subsequently constructed for the TLAS leaf node. Forexample, a graph cut applied immediately below the BLAS root node of aTLAS leaf node would result in a world-space AABB with a relatively lowdegree of tightness (e.g., because the world-space AABB generated forthe TLAS leaf node is built around the vertices of the BLAS root node'sAABB).

In some examples, a graph cut applied immediately above the BLAS leafnodes would result in a world-space AABB with a relatively high degreeof tightness (e.g., because the BLAS leaf nodes contain the individualprimitives of the BLAS, the world-space AABB generated for the TLAS leafnode is built around the vertices of each individual primitive). In somecases, applying a graph cut immediately above the BLAS leaf nodes canresult in the same world-space AABB as is generated according to thefirst approach described above (e.g., because both approaches transformeach vertex of the individual primitives into world-space vertices thatare then used to generate a maximally tight world-space AABB).

In some cases, graph cut selection can therefore offer a tunableselection in the tradeoff between world-space AABB versus compute time.A larger amount of compute time is needed to build a BVH with tightAABBs than loose AABBs; however, tighter AABBs allow subsequent raytracing to be performed in less compute time. In an illustrativeexample, graph cut selection can be performed based at least in part onone or more cost metrics indicating the amount of available compute timefor BVH and/or AABB building and the amount of available compute timefor ray tracing. Graph cut selection can additionally be based on aprediction or understanding of how often the bottom level BVH andworld-space AABBs might be rebuilt for a given scene object, as a fastBVH and AABB build time may be needed for scene objects that deform orotherwise require frequent BVH rebuilds. In some examples, a particularapproach can be selected or configured as described above based on aknown or determined BVH build time metric, e.g., such that anappropriate BVH and/or a tightest world-space AABBs can be constructedsubject to the constraint of maximum build time given by the BVH buildtime metric.

FIG. 10 is a flowchart illustrating an example of a process 1000 forgraphics processing. Although the example process 1000 depicts aparticular sequence of operations, the sequence may be altered withoutdeparting from the scope of the present disclosure. For example, some ofthe operations depicted may be performed in parallel or in a differentsequence that does not materially affect the function of the process1000. In other examples, different components of an example device orsystem that implements the process 1000 may perform functions atsubstantially the same time or in a specific sequence.

At block 1002, the process 1000 includes obtaining an acceleration datastructure. In some examples, the acceleration data structure includesone or more primitives of a scene object. For example, the accelerationdata structure can be obtained by or from the acceleration datastructure engine 622 associated with the ray tracing system 600illustrated in FIG. 6 . In some cases, the acceleration data structurecan include a bounding volume hierarchy (BVH). In some examples, theacceleration data structure can include a bottom-level accelerationstructure (BLAS). For example, the acceleration data structure caninclude one or more of the acceleration data structure 900 a illustratedin FIG. 9A and/or the acceleration data structure 900 b illustrated inFIG. 9B. In some cases, the one or more primitives of the scene objectcan be included in one or more leaf nodes of the acceleration datastructure. For example, one or more of the leaf nodes 928 and 932-937 ofthe acceleration data structure 900 a illustrated in FIG. 9A and/or ofthe acceleration data structure 900 b illustrated in FIG. 9B can includethe one or more primitives of the scene object.

In some examples, the acceleration data structure can include a BLASthat is associated with a top-level acceleration structure (TLAS) leafnode. In examples where the acceleration data structure includes a BLAS,the BLAS can additionally, or alternatively, include one or moreintermediate BLAS nodes. For example, the one or more intermediate BLASnodes can include one or more of the BLAS child nodes 912, 922, 924and/or 926 of the acceleration data structure 900 a illustrated in FIG.9A and/or of the acceleration data structure 900 b illustrated in FIG.9B. One or more of the intermediate BLAS nodes can include anaxis-aligned bounding box (AABB) encompassing a subset of the one ormore primitives of the scene object.

At block 1004, the process 1000 includes applying a graph cut to theacceleration data structure. In some examples, the graph cut can beapplied directly above or directly below a plurality of leaf nodes ofthe acceleration data structure. In some cases, when the accelerationdata structure is a TLAS and/or a BLAS, the graph cut can be appliedacross the bottom level BVH (e.g., BLAS) included in a given TLAS leafnode. Applying the graph cut can partition the nodes of the accelerationdata structure into two disjoint subsets, such that any path from theroot node of the acceleration data structure to a leaf node of theacceleration data structure crosses the graph cut line exactly once. Forexample, applying the graph cut to the acceleration data structure caninclude applying the graph cut line 950 a illustrated in FIG. 9A or thegraph cut line 950 b illustrated in FIG. 9B. In some cases, any graphcut across a bottom level BVH or acceleration data structure can be usedto determine a set of bounding boxes (e.g., AABBs) that contain theentire geometry (e.g., the primitives included in the acceleration datastructure) of the scene object associated with the acceleration datastructure.

At block 1006, the process 1000 includes determining a set of nodes ofthe acceleration data structure based on the graph cut. In someexamples, the set of nodes is located adjacent to the graph cut. Forexample, the set of nodes determined based on the graph cut can includethe one or more nodes of the acceleration data structure that arelocated immediately above the graph cut line. In some cases, the set ofnodes determined based on the graph cut can include the one or morenodes of the acceleration data structure that are located immediatelybelow the graph cut line.

In some examples, the set of nodes determined based on the graph cut caninclude a plurality of leaf nodes of the acceleration data structure.The plurality of leaf nodes can include each vertex of the scene objectassociated with the acceleration data structure. For example, the set ofnodes determined based on the graph cut can include the nodes 922, 924,925, 936, 937, and 928 illustrated in FIG. 9A as being locatedimmediately below the graph cut line 950 a. In another example, the setof nodes determined based on the graph cut can include the nodes 932,933, 924, 936, 937, and 928 illustrated in FIG. 9B as being locatedimmediately below the graph cut line 950 b.

In some examples, at block 1006, the process 1000 can further includedetermining one or more child nodes of a root node of the accelerationdata structure and determining a Surface Area Heuristic (SAH) for eachchild node. The graph cut can be applied to the acceleration datastructure based on the determined SAH for each child node. For example,the one or more child nodes can be determined based on the graph cutand/or graph cut line (e.g., as described above). In some cases, anoptimal graph cut for a given computational cost budget can bedetermined using the SAH. For example, the SAH can be applied to treeletgrowth of the acceleration data structure for the given computationalcost budget. In some cases, an iterative technique can be used todetermine the optimal graph cut to apply to the acceleration datastructure. For example, the iterative technique can include placing theroot node of the acceleration data structure in a stack and selectivelyexpanding the root node and its child nodes (e.g., by popping the stack)based on their SAH until the number of nodes in the stack reaches thegiven computational budget. In some examples, the root node of theacceleration data structure can be placed in the stack 960 illustratedin FIGS. 9C-9E. The stack (e.g., stack 960) can be included in thememory 616 illustrated in the ray tracing system 600 of FIG. 6 .

At block 1008, the process 1000 includes generating a world-spacebounding box for the scene object (e.g., the scene object associatedwith the acceleration data structure). In some examples, the world-spacebounding box is generated for the set of nodes determined based on thegraph cut. For example, the generated world-space bounding box caninclude one or more of the world-space bounding boxes 830, 850, and/or870 illustrated in FIGS. 8A-8C, respectively. In some cases, theworld-space bounding box generated for the scene object can be aworld-space axis-aligned bounding box (AABB).

In some examples, at block 1008, the process 1000 can include obtaininga respective object-space bounding box for each node of the set of nodesdetermined based on the graph cut. Each respective object-space boundingbox of each node (e.g., each node of the set of nodes determined basedon the graph cut) can be transformed into a plurality of world-spacevertices. In some examples, the world-space bounding box for the sceneobject can be generated using the transformed plurality of world-spacevertices.

In some examples, the processes described herein (e.g., process 1000and/or any other process described herein) may be performed by acomputing device, apparatus, or system. In one example, the process 1000can be performed by a computing device or system having the computingdevice architecture 1100 of FIG. 11 . The computing device, apparatus,or system can include any suitable device, such as a mobile device(e.g., a mobile phone), a desktop computing device, a tablet computingdevice, a wearable device (e.g., a VR headset, an AR headset, ARglasses, an extended reality (XR) device (e.g., a VR headset or HMD, anAR headset, HMD, or glasses, etc.), a network-connected watch orsmartwatch, or other wearable device), a server computer, a vehicle(e.g., autonomous or non-autonomous vehicle) or computing device of avehicle, a robotic device, a laptop computer, a smart television, acamera, and/or any other computing device with the resource capabilitiesto perform the processes described herein, including the process 1000and/or any other process described herein. In some cases, the computingdevice or apparatus may include various components, such as one or moreinput devices, one or more output devices, one or more processors, oneor more microprocessors, one or more microcomputers, one or morecameras, one or more sensors, and/or other component(s) that areconfigured to carry out the steps of processes described herein. In someexamples, the computing device may include a display, a networkinterface configured to communicate and/or receive the data, anycombination thereof, and/or other component(s). The network interfacemay be configured to communicate and/or receive Internet Protocol (IP)based data or other type of data.

The components of the computing device can be implemented in circuitry.For example, the components can include and/or can be implemented usingelectronic circuits or other electronic hardware, which can include oneor more programmable electronic circuits (e.g., microprocessors,graphics processing units (GPUs), digital signal processors (DSPs),central processing units (CPUs), and/or other suitable electroniccircuits), and/or can include and/or be implemented using computersoftware, firmware, or any combination thereof, to perform the variousoperations described herein.

The process 1000 is illustrated as a logical flow diagram, the operationof which represents a sequence of operations that can be implemented inhardware, computer instructions, or a combination thereof. In thecontext of computer instructions, the operations representcomputer-executable instructions stored on one or more computer-readablestorage media that, when executed by one or more processors, perform therecited operations. Generally, computer-executable instructions includeroutines, programs, objects, components, data structures, and the likethat perform particular functions or implement particular data types.The order in which the operations are described is not intended to beconstrued as a limitation, and any number of the described operationscan be combined in any order and/or in parallel to implement theprocesses.

Additionally, the process 1000 and/or any other process described hereinmay be performed under the control of one or more computer systemsconfigured with executable instructions and may be implemented as code(e.g., executable instructions, one or more computer programs, or one ormore applications) executing collectively on one or more processors, byhardware, or combinations thereof. As noted above, the code may bestored on a computer-readable or machine-readable storage medium, forexample, in the form of a computer program comprising a plurality ofinstructions executable by one or more processors. The computer-readableor machine-readable storage medium may be non-transitory.

FIG. 11 illustrates an example computing device architecture 1100 of anexample computing device which can implement the various techniquesdescribed herein. In some examples, the computing device can include amobile device, a wearable device, an extended reality device (e.g., avirtual reality (VR) device, an augmented reality (AR) device, anextended reality (XR) device, or a mixed reality (MR) device), apersonal computer, a laptop computer, a video server, a vehicle (orcomputing device of a vehicle), or other device. The components ofcomputing device architecture 1100 are shown in electrical communicationwith each other using connection 1105, such as a bus. The examplecomputing device architecture 1100 includes a processing unit (CPU orprocessor) 1110 and computing device connection 1105 that couplesvarious computing device components including computing device memory1115, such as read only memory (ROM) 1120 and random-access memory (RAM)1125, to processor 1110.

Computing device architecture 1100 can include a cache of high-speedmemory connected directly with, in close proximity to, or integrated aspart of processor 1110 Computing device architecture 1100 can copy datafrom memory 1115 and/or the storage device 1130 to cache 1112 for quickaccess by processor 1110. In this way, the cache can provide aperformance boost that avoids processor 1110 delays while waiting fordata. These and other engines can control or be configured to controlprocessor 1110 to perform various actions. Other computing device memory1115 may be available for use as well. Memory 1115 can include multipledifferent types of memory with different performance characteristics.Processor 1110 can include any general-purpose processor and a hardwareor software service, such as service 1 1132, service 2 1134, and service3 1136 stored in storage device 1130, configured to control processor1110 as well as a special-purpose processor where software instructionsare incorporated into the processor design. Processor 1110 may be aself-contained system, containing multiple cores or processors, a bus,memory controller, cache, etc. A multi-core processor may be symmetricor asymmetric.

To enable user interaction with the computing device architecture 1100,input device 1145 can represent any number of input mechanisms, such asa microphone for speech, a touch-sensitive screen for gesture orgraphical input, keyboard, mouse, motion input, speech and so forth.Output device 1135 can also be one or more of a number of outputmechanisms known to those of skill in the art, such as a display,projector, television, speaker device, etc. In some instances,multimodal computing devices can enable a user to provide multiple typesof input to communicate with computing device architecture 1100.Communication interface 1040 can generally govern and manage the userinput and computing device output. There is no restriction on operatingon any particular hardware arrangement and therefore the basic featureshere may easily be substituted for improved hardware or firmwarearrangements as they are developed.

Storage device 1130 is a non-volatile memory and can be a hard disk orother types of computer readable media which can store data that areaccessible by a computer, such as magnetic cassettes, flash memorycards, solid state memory devices, digital versatile disks, cartridges,random access memories (RAMs) 1125, read only memory (ROM) 1120, andhybrids thereof. Storage device 1130 can include services 1132, 1134,1136 for controlling processor 1110. Other hardware or software modulesor engines are contemplated. Storage device 1130 can be connected to thecomputing device connection 1105. In one aspect, a hardware module thatperforms a particular function can include the software component storedin a computer-readable medium in connection with the necessary hardwarecomponents, such as processor 1110, connection 1105, output device 1135,and so forth, to carry out the function.

Aspects of the present disclosure are applicable to any suitableelectronic device (such as security systems, smartphones, tablets,laptop computers, vehicles, drones, or other devices) including orcoupled to one or more active depth sensing systems. While describedbelow with respect to a device having or coupled to one light projector,aspects of the present disclosure are applicable to devices having anynumber of light projectors and are therefore not limited to specificdevices.

The term “device” is not limited to one or a specific number of physicalobjects (such as one smartphone, one controller, one processing systemand so on). As used herein, a device may be any electronic device withone or more parts that may implement at least some portions of thisdisclosure. While the below description and examples use the term“device” to describe various aspects of this disclosure, the term“device” is not limited to a specific configuration, type, or number ofobjects. Additionally, the term “system” is not limited to multiplecomponents or specific aspects. For example, a system may be implementedon one or more printed circuit boards or other substrates and may havemovable or static components. While the below description and examplesuse the term “system” to describe various aspects of this disclosure,the term “system” is not limited to a specific configuration, type, ornumber of objects.

Specific details are provided in the description above to provide athorough understanding of the aspects and examples provided herein.However, it will be understood by one of ordinary skill in the art thatthe aspects may be practiced without these specific details. For clarityof explanation, in some instances the present technology may bepresented as including individual functional blocks including functionalblocks comprising devices, device components, steps or routines in amethod embodied in software, or combinations of hardware and software.Additional components may be used other than those shown in the figuresand/or described herein. For example, circuits, systems, networks,processes, and other components may be shown as components in blockdiagram form in order not to obscure the aspects in unnecessary detail.In other instances, well-known circuits, processes, algorithms,structures, and techniques may be shown without unnecessary detail inorder to avoid obscuring the aspects.

Individual aspects may be described above as a process or method whichis depicted as a flowchart, a flow diagram, a data flow diagram, astructure diagram, or a block diagram. Although a flowchart may describethe operations as a sequential process, many of the operations can beperformed in parallel or concurrently. In addition, the order of theoperations may be re-arranged. A process is terminated when itsoperations are completed, but could have additional steps not includedin a figure. A process may correspond to a method, a function, aprocedure, a subroutine, a subprogram, etc. When a process correspondsto a function, its termination can correspond to a return of thefunction to the calling function or the main function.

Processes and methods according to the above-described examples can beimplemented using computer-executable instructions that are stored orotherwise available from computer-readable media. Such instructions caninclude, for example, instructions and data which cause or otherwiseconfigure a general-purpose computer, special purpose computer, or aprocessing device to perform a certain function or group of functions.Portions of computer resources used can be accessible over a network.The computer executable instructions may be, for example, binaries,intermediate format instructions such as assembly language, firmware,source code, etc.

The term “computer-readable medium” includes, but is not limited to,portable or non-portable storage devices, optical storage devices, andvarious other mediums capable of storing, containing, or carryinginstruction(s) and/or data. A computer-readable medium may include anon-transitory medium in which data can be stored and that does notinclude carrier waves and/or transitory electronic signals propagatingwirelessly or over wired connections. Examples of a non-transitorymedium may include, but are not limited to, a magnetic disk or tape,optical storage media such as flash memory, memory or memory devices,magnetic or optical disks, flash memory, USB devices provided withnon-volatile memory, networked storage devices, compact disk (CD) ordigital versatile disk (DVD), any suitable combination thereof, amongothers. A computer-readable medium may have stored thereon code and/ormachine-executable instructions that may represent a procedure, afunction, a subprogram, a program, a routine, a subroutine, a module, anengine, a software package, a class, or any combination of instructions,data structures, or program statements. A code segment may be coupled toanother code segment or a hardware circuit by passing and/or receivinginformation, data, arguments, parameters, or memory contents.Information, arguments, parameters, data, etc. may be passed, forwarded,or transmitted via any suitable means including memory sharing, messagepassing, token passing, network transmission, or the like.

In some aspects the computer-readable storage devices, mediums, andmemories can include a cable or wireless signal containing a bit streamand the like. However, when mentioned, non-transitory computer-readablestorage media expressly exclude media such as energy, carrier signals,electromagnetic waves, and signals per se.

Devices implementing processes and methods according to thesedisclosures can include hardware, software, firmware, middleware,microcode, hardware description languages, or any combination thereof,and can take any of a variety of form factors. When implemented insoftware, firmware, middleware, or microcode, the program code or codesegments to perform the necessary tasks (e.g., a computer-programproduct) may be stored in a computer-readable or machine-readablemedium. A processor(s) may perform the necessary tasks. Typical examplesof form factors include laptops, smart phones, mobile phones, tabletdevices or other small form factor personal computers, personal digitalassistants, rackmount devices, standalone devices, and so on.Functionality described herein also can be embodied in peripherals oradd-in cards. Such functionality can also be implemented on a circuitboard among different chips or different processes executing in a singledevice, by way of further example.

The instructions, media for conveying such instructions, computingresources for executing them, and other structures for supporting suchcomputing resources are example means for providing the functionsdescribed in the disclosure.

In the foregoing description, aspects of the application are describedwith reference to specific aspects thereof, but those skilled in the artwill recognize that the application is not limited thereto. Thus, whileillustrative aspects of the application have been described in detailherein, it is to be understood that the inventive concepts may beotherwise variously embodied and employed, and that the appended claimsare intended to be construed to include such variations, except aslimited by the prior art. Various features and aspects of theabove-described application may be used individually or jointly.Further, aspects can be utilized in any number of environments andapplications beyond those described herein without departing from thebroader spirit and scope of the specification. The specification anddrawings are, accordingly, to be regarded as illustrative rather thanrestrictive. For the purposes of illustration, methods were described ina particular order. It should be appreciated that in alternate aspects,the methods may be performed in a different order than that described.

One of ordinary skill will appreciate that the less than (“<”) andgreater than (“>”) symbols or terminology used herein can be replacedwith less than or equal to (“≤”) and greater than or equal to (“≥”)symbols, respectively, without departing from the scope of thisdescription.

Where components are described as being “configured to” perform certainoperations, such configuration can be accomplished, for example, bydesigning electronic circuits or other hardware to perform theoperation, by programming programmable electronic circuits (e.g.,microprocessors, or other suitable electronic circuits) to perform theoperation, or any combination thereof.

The phrase “coupled to” refers to any component that is physicallyconnected to another component either directly or indirectly, and/or anycomponent that is in communication with another component (e.g.,connected to the other component over a wired or wireless connection,and/or other suitable communication interface) either directly orindirectly.

Claim language or other language reciting “at least one of” a set and/or“one or more” of a set indicates that one member of the set or multiplemembers of the set (in any combination) satisfy the claim. For example,claim language reciting “at least one of A and B” or “at least one of Aor B” means A, B, or A and B. In another example, claim languagereciting “at least one of A, B, and C” or “at least one of A, B, or C”means A, B, C, or A and B, or A and C, or B and C, or A and B and C. Thelanguage “at least one of” a set and/or “one or more” of a set does notlimit the set to the items listed in the set. For example, claimlanguage reciting “at least one of A and B” or “at least one of A or B”can mean A, B, or A and B, and can additionally include items not listedin the set of A and B.

The various illustrative logical blocks, modules, engines, circuits, andalgorithm steps described in connection with the aspects disclosedherein may be implemented as electronic hardware, computer software,firmware, or combinations thereof. To clearly illustrate thisinterchangeability of hardware and software, various illustrativecomponents, blocks, modules, engines, circuits, and steps have beendescribed above generally in terms of their functionality. Whether suchfunctionality is implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem. Skilled artisans may implement the described functionality invarying ways for each particular application, but such implementationdecisions should not be interpreted as causing a departure from thescope of the present application.

The techniques described herein may also be implemented in electronichardware, computer software, firmware, or any combination thereof. Suchtechniques may be implemented in any of a variety of devices such asgeneral purposes computers, wireless communication device handsets, orintegrated circuit devices having multiple uses including application inwireless communication device handsets and other devices. Any featuresdescribed as modules or components may be implemented together in anintegrated logic device or separately as discrete but interoperablelogic devices. If implemented in software, the techniques may berealized at least in part by a computer-readable data storage mediumcomprising program code including instructions that, when executed,performs one or more of the methods described above. Thecomputer-readable data storage medium may form part of a computerprogram product, which may include packaging materials. Thecomputer-readable medium may comprise memory or data storage media, suchas random-access memory (RAM) such as synchronous dynamic random-accessmemory (SDRAM), read-only memory (ROM), non-volatile random-accessmemory (NVRAM), electrically erasable programmable read-only memory(EEPROM), FLASH memory, magnetic or optical data storage media, and thelike. The techniques additionally, or alternatively, may be realized atleast in part by a computer-readable communication medium that carriesor communicates program code in the form of instructions or datastructures and that can be accessed, read, and/or executed by acomputer, such as propagated signals or waves.

The program code may be executed by a processor, which may include oneor more processors, such as one or more digital signal processors(DSPs), general purpose microprocessors, an application specificintegrated circuits (ASICs), field programmable logic arrays (FPGAs), orother equivalent integrated or discrete logic circuitry. Such aprocessor may be configured to perform any of the techniques describedin this disclosure. A general-purpose processor may be a microprocessor;but in the alternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration. Accordingly, the term “processor,” as used herein mayrefer to any of the foregoing structure, any combination of theforegoing structure, or any other structure or apparatus suitable forimplementation of the techniques described herein.

Illustrative aspects of the disclosure include:

Aspect 1: A method of ray tracing, the method comprising: obtaining anacceleration data structure, the acceleration data structure includingone or more primitives of a scene object; applying a graph cut to theacceleration data structure; determining a set of nodes of theacceleration data structure based on the graph cut, wherein the set ofnodes is located adjacent to the graph cut; and generating a world-spacebounding box for the scene object, wherein the world-space bounding boxis generated for the set of nodes determined based on the graph cut.

Aspect 2: The method of Aspect 1, further comprising: obtaining arespective object-space bounding box for each node of the set of nodes;and transforming each respective object-space bounding box of each nodeinto a plurality of world-space vertices.

Aspect 3: The method of Aspect 2, wherein the world-space bounding boxfor the scene object is generated based on the plurality of world-spacevertices.

Aspect 4: The method of any of Aspects 1 to 3, further comprising:determining one or more child nodes of a root node of the accelerationdata structure; determining a Surface Area Heuristic (SAH) for eachchild node of the one or more child nodes; and applying the graph cut tothe acceleration data structure based on the determined SAH for eachchild node.

Aspect 5: The method of Aspect 4, further comprising: determining acomputational cost budget specifying a maximum number of nodes in theset of nodes based on the graph cut; and determining the SAH for eachchild node of the one or more child nodes based on the determinedcomputational cost.

Aspect 6: The method of any of Aspects 1 to 5, wherein the graph cut isapplied directly above or directly below a plurality of leaf nodes ofthe acceleration data structure.

Aspect 7: The method of any of Aspects 1 to 6, wherein: the set of nodesdetermined based on the graph cut includes a plurality of leaf nodes ofthe acceleration data structure, wherein the plurality of leaf nodesincludes each vertex of the scene object.

Aspect 8: The method of Aspect 7, wherein the world-space bounding boxis generated based at least in part on transforming each vertex of thescene object from an object-space representation into a world-spacerepresentation.

Aspect 9: The method of any of Aspects 1 to 8, wherein the one or moreprimitives of the scene object are included in one or more leaf nodes ofthe acceleration data structure.

Aspect 10: The method of any of Aspects 1 to 9, wherein the world-spacebounding box generated for the scene object is a world-spaceaxis-aligned bounding box (AABB).

Aspect 11: The method of any of Aspects 1 to 10, wherein theacceleration data structure includes a bounding volume hierarchy (BVH).

Aspect 12: The method of any of Aspects 1 to 11, wherein theacceleration data structure includes a bottom-level accelerationstructure (BLAS).

Aspect 13: The method of Aspect 12, wherein the BLAS: is associated witha top-level acceleration structure (TLAS) leaf node; and includes one ormore intermediate BLAS nodes, each intermediate BLAS node including anaxis-aligned bounding box (AABB) encompassing a subset of the one ormore primitives of the scene object.

Aspect 14: The method of any of Aspects 1 to 13, wherein the set ofnodes located adjacent to the graph cut is located above the graph cutor below the graph cut.

Aspect 15: A method of ray tracing, the method comprising: obtaining abottom-level acceleration structure (BLAS), the BLAS including one ormore primitives of a scene object; calculating a proxy geometry for aplurality of vertices of the BLAS, the proxy geometry having a firstnumber of vertices that is smaller than a number of vertices containedin the BLAS; transforming the first number of vertices of the proxygeometry into a plurality of proxy geometry world-space vertices; andgenerating a world-space axis-aligned bounding box (AABB) for the BLAS,wherein the world-space axis-aligned bounding box encloses the pluralityof proxy geometry world-space vertices.

Aspect 16: The method of Aspect 15, wherein the proxy geometry is aconvex hull or an approximation of a convex hull.

Aspect 17: A method of ray tracing, the method comprising: obtaining abottom-level acceleration structure (BLAS), the BLAS including aplurality of object-space vertices for one or more primitives of a sceneobject; transforming each vertex of the plurality of object-spacevertices into a transformed world-space vertex; and generating aworld-space axis-aligned bounding box (AABB) for the BLAS such that theworld-space AABB encloses each transformed world-space vertex.

Aspect 18: An apparatus for ray tracing, comprising: a memory; and oneor more processors coupled to the memory, the one or more processorsconfigured to: obtain an acceleration data structure, the accelerationdata structure including one or more primitives of a scene object, applya graph cut to the acceleration data structure, determine a set of nodesof the acceleration data structure based on the graph cut, wherein theset of nodes is located adjacent to the graph cut, and generate aworld-space bounding box for the scene object, wherein the world-spacebounding box is generated for the set of nodes determined based on thegraph cut.

Aspect 19: The apparatus of Aspect 18, wherein the one or moreprocessors are configured to: obtain a respective object-space boundingbox for each node of the set of nodes; and transform each respectiveobject-space bounding box of each node into a plurality of world-spacevertices.

Aspect 20: The apparatus of Aspect 19, wherein the world-space boundingbox for the scene object is generated based on the plurality ofworld-space vertices.

Aspect 21: The apparatus of any of Aspects 18 to 20, wherein the one ormore processors are configured to: determine one or more child nodes ofa root node of the acceleration data structure; determine a Surface AreaHeuristic (SAH) for each child node of the one or more child nodes; andapply the graph cut to the acceleration data structure based on thedetermined SAH for each child node.

Aspect 22: The apparatus of Aspect 21, wherein the one or moreprocessors are configured to: determine a computational cost budgetspecifying a maximum number of nodes in the set of nodes based on thegraph cut; and determine the SAH for each child node of the one or morechild nodes based on the determined computational cost.

Aspect 23: The apparatus of any of Aspects 18 to 22, wherein the graphcut is applied directly above or directly below a plurality of leafnodes of the acceleration data structure.

Aspect 24: The apparatus of any of Aspects 18 to 23, wherein the set ofnodes determined based on the graph cut includes a plurality of leafnodes of the acceleration data structure, wherein the plurality of leafnodes includes each vertex of the scene object.

Aspect 25: The apparatus of Aspect 24, wherein the world-space boundingbox is generated based at least in part on transforming each vertex ofthe scene object from an object-space representation into a world-spacerepresentation.

Aspect 26: The apparatus of any of Aspects 18 to 25, wherein the one ormore primitives of the scene object are included in one or more leafnodes of the acceleration data structure.

Aspect 27: The apparatus of any of Aspects 18 to 26, wherein theworld-space bounding box generated for the scene object is a world-spaceaxis-aligned bounding box (AABB).

Aspect 28: The apparatus of any of Aspects 18 to 27, wherein theacceleration data structure includes a bounding volume hierarchy (BVH).

Aspect 29: The apparatus of any of Aspects 18 to 28, wherein theacceleration data structure includes a bottom-level accelerationstructure (BLAS).

Aspect 30: The apparatus of Aspect 29, wherein the BLAS: is associatedwith a top-level acceleration structure (TLAS) leaf node; and includesone or more intermediate BLAS nodes, each intermediate BLAS nodeincluding an axis-aligned bounding box (AABB) encompass a subset of theone or more primitives of the scene object.

Aspect 31: The apparatus of any of Aspects 18 to 30, wherein the set ofnodes located adjacent to the graph cut is located above the graph cutor below the graph cut.

Aspect 32: An apparatus for ray tracing, comprising: a memory; and oneor more processors coupled to the memory, the one or more processorsconfigured to: obtain a bottom-level acceleration structure (BLAS), theBLAS including one or more primitives of a scene object; calculate aproxy geometry for a plurality of vertices of the BLAS, the proxygeometry having a first number of vertices that is smaller than a numberof vertices contained in the BLAS; transform the first number ofvertices of the proxy geometry into a plurality of proxy geometryworld-space vertices; and generate a world-space axis-aligned boundingbox (AABB) for the BLAS, wherein the world-space axis-aligned boundingbox encloses the plurality of proxy geometry world-space vertices.

Aspect 33: The apparatus of Aspect 32, wherein the proxy geometry is aconvex hull or an approximation of a convex hull.

Aspect 34: An apparatus for ray tracing, comprising: a memory; and oneor more processors coupled to the memory, the one or more processorsconfigured to: obtain a bottom-level acceleration structure (BLAS), theBLAS including a plurality of object-space vertices for one or moreprimitives of a scene object; transform each vertex of the plurality ofobject-space vertices into a transformed world-space vertex; andgenerate a world-space axis-aligned bounding box (AABB) for the BLASsuch that the world-space AABB encloses each transformed world-spacevertex.

Aspect 35: A non-transitory computer-readable storage medium havingstored thereon instructions which, when executed by one or moreprocessors, cause the one or more processors to perform any of theoperations of Aspects 1 to 14 and Aspects 18 to 31.

Aspect 36: An apparatus comprising means for performing any of theoperations of Aspects 1 to 14 and Aspects 18 to 31.

Aspect 37: A non-transitory computer-readable storage medium havingstored thereon instructions which, when executed by one or moreprocessors, cause the one or more processors to perform any of theoperations of Aspects 15 to 16 and Aspects 32 to 33.

Aspect 38: An apparatus comprising means for performing any of theoperations of Aspects 15 to 16 and Aspects 32 to 33.

Aspect 39: A non-transitory computer-readable storage medium havingstored thereon instructions which, when executed by one or moreprocessors, cause the one or more processors to perform any of theoperations of Aspects 17 and 34.

Aspect 40: An apparatus comprising means for performing any of theoperations of Aspects 17 and 34.

What is claimed is:
 1. A method of ray tracing, the method comprising:obtaining an acceleration data structure, the acceleration datastructure including one or more primitives of a scene object;determining one or more child nodes of a root node of the accelerationdata structure; determining a Surface Area Heuristic (SAH) for eachchild node of the one or more child nodes; determining a computationalbudget corresponding to a maximum number of nodes for a graph cut;determining the graph cut based on the determined SAH for each childnode and the computational budget; applying the graph cut to theacceleration data structure; determining a set of nodes of theacceleration data structure based on the graph cut, wherein the set ofnodes is located adjacent to the graph cut; and generating a world-spacebounding box for the scene object, wherein the world-space bounding boxis generated for the set of nodes determined based on the graph cut. 2.The method of claim 1, further comprising: obtaining a respectiveobject-space bounding box for each node of the set of nodes; andtransforming each respective object-space bounding box of each node intoa plurality of world-space vertices.
 3. The method of claim 2, whereinthe world-space bounding box for the scene object is generated based onthe plurality of world-space vertices.
 4. The method of claim 1, whereinthe graph cut is applied directly above or directly below a plurality ofleaf nodes of the acceleration data structure.
 5. The method of claim 1,wherein the set of nodes determined based on the graph cut includes aplurality of leaf nodes of the acceleration data structure, and whereinthe plurality of leaf nodes includes each vertex of the scene object. 6.The method of claim 5, wherein the world-space bounding box is generatedbased at least in part on transforming each vertex of the scene objectfrom an object-space representation into a world-space representation.7. The method of claim 1, wherein the one or more primitives of thescene object are included in one or more leaf nodes of the accelerationdata structure.
 8. The method of claim 1, wherein the world-spacebounding box generated for the scene object is a world-spaceaxis-aligned bounding box (AABB).
 9. The method of claim 1, wherein theacceleration data structure includes a bounding volume hierarchy (BVH).10. The method of claim 1, wherein the acceleration data structureincludes a bottom-level acceleration structure (BLAS).
 11. The method ofclaim 10, wherein the BLAS: is associated with a top-level accelerationstructure (TLAS) leaf node; and includes one or more intermediate BLASnodes, each intermediate BLAS node including an axis-aligned boundingbox (AABB) encompassing a subset of the one or more primitives of thescene object.
 12. The method of claim 1, wherein the set of nodeslocated adjacent to the graph cut is located above the graph cut orbelow the graph cut.
 13. An apparatus for ray tracing, comprising: amemory; and one or more processors coupled to the memory, the one ormore processors configured to: obtain an acceleration data structure,the acceleration data structure including one or more primitives of ascene object; determine one or more child nodes of a root node of theacceleration data structure; determine a Surface Area Heuristic (SAH)for each child node of the one or more child nodes; determine acomputational budget that corresponds to a maximum number of nodes for agraph cut; determine the graph cut based on the determined SAH for eachchild node and the computational budget; apply the graph cut to theacceleration data structure; determine a set of nodes of theacceleration data structure based on the graph cut, wherein the set ofnodes is located adjacent to the graph cut; and generate a world-spacebounding box for the scene object, wherein the world-space bounding boxis generated for the set of nodes determined based on the graph cut. 14.The apparatus of claim 13, wherein the one or more processors areconfigured to: obtain a respective object-space bounding box for eachnode of the set of nodes; and transform each respective object-spacebounding box of each node into a plurality of world-space vertices. 15.The apparatus of claim 14, wherein the world-space bounding box for thescene object is generated based on the plurality of world-spacevertices.
 16. The apparatus of claim 13, wherein the graph cut isapplied directly above or directly below a plurality of leaf nodes ofthe acceleration data structure.
 17. The apparatus of claim 13, whereinthe set of nodes determined based on the graph cut includes a pluralityof leaf nodes of the acceleration data structure, and wherein theplurality of leaf nodes includes each vertex of the scene object. 18.The apparatus of claim 17, wherein the world-space bounding box isgenerated based at least in part on transforming each vertex of thescene object from an object-space representation into a world-spacerepresentation.
 19. The apparatus of claim 13, wherein the one or moreprimitives of the scene object are included in one or more leaf nodes ofthe acceleration data structure.
 20. The apparatus of claim 13, whereinthe world-space bounding box generated for the scene object is aworld-space axis-aligned bounding box (AABB).
 21. The apparatus of claim13, wherein the acceleration data structure includes a bounding volumehierarchy (BVH).
 22. The apparatus of claim 13, wherein the accelerationdata structure includes a bottom-level acceleration structure (BLAS).23. The apparatus of claim 22, wherein the BLAS: is associated with atop-level acceleration structure (TLAS) leaf node; and includes one ormore intermediate BLAS nodes, each intermediate BLAS node including anaxis-aligned bounding box (AABB) encompassing a subset of the one ormore primitives of the scene object.
 24. The apparatus of claim 13,wherein the set of nodes located adjacent to the graph cut is locatedabove the graph cut or below the graph cut.
 25. A non-transitorycomputer-readable medium having stored thereon instructions that, whenexecuted by one or more processors, cause the one or more processors to:obtain an acceleration data structure, the acceleration data structureincluding one or more primitives of a scene object; determine one ormore child nodes of a root node of the acceleration data structure;determine a Surface Area Heuristic (SAH) for each child node of the oneor more child nodes; determine a computational budget that correspondsto a maximum number of nodes for a graph cut; determine the graph cutbased on the determined SAH for each child node and the computationalbudget; apply the graph cut to the acceleration data structure;determine a set of nodes of the acceleration data structure based on thegraph cut, wherein the set of nodes is located adjacent to the graphcut; and generate a world-space bounding box for the scene object,wherein the world-space bounding box is generated for the set of nodesdetermined based on the graph cut.
 26. The non-transitorycomputer-readable medium of claim 25, further comprising instructionsthat, when executed by the one or more processors, cause the one or moreprocessors to: obtain a respective object-space bounding box for eachnode of the set of nodes; and transform each respective object-spacebounding box of each node into a plurality of world-space vertices.